1. Field of the Invention
The present invention generally relates to an actuator that is incorporated into an input device such as a mouse used in conjunction with a personal computer, and more particularly, to an actuator that includes a mobile unit to move in-plane by virtue of magnetic force and can perform accurate coordinate input.
2. Description of the Related Art
Conventionally, small-sized actuators each having a mobile unit that moves in-plane by virtue of magnetic force have been developed. Such actuators are expected to be novel devices for transmitting various types of information from computers to operators. For example, an actuator of the above kind can be incorporated into a mouse that is normally used in conjunction with a personal computer. A conventional mouse has been used as an input device for performing input from an operator to a computer. In a case where the above actuator is incorporated into a conventional mouse, signals generated from the computer can be transmitted to an operator. In this manner, the conventional mouse can be used as a man-machine interface.
Japanese Unexamined Patent Publication No. 10-117470 (hereinafter referred to as Patent Document 1) discloses a small-sized actuator of the in-plane mobile type. This actuator includes a coil unit that has a small loop coil and a large loop coil arranged in one plane, and a magnet unit that has four permanent magnets secured onto a base plate. The four permanent magnets generate magnetic flux that crosses the loop coils in a chain-like fashion. In this actuator, relative motion can be caused between the coil unit and the magnet unit that are maintained in parallel with each other. Either the coil unit or the magnet unit can be moved in the plane by virtue of a thrust force that is generated at the time of energizing the loop coils.
Patent Document 1 also discloses a structure in which a scale magnet for position detection is attached to the mobile magnet body, and a MR sensor is fixed in such a position as to face the scale magnet and to perform position detection. With this structure, feedback control is performed with signals supplied from the MR sensor, so that the mobile unit can be moved to a desired position.
An input device such as a mouse is naturally required to have a function of performing coordinate input. Therefore, the above described actuator having a mobile unit that moves in a plane upon receipt of a signal from the outside should have a structure as an input device.
The actuator disclosed in Patent Document 1, however, is a device that is to be incorporated into an optical apparatus, for example. In an optical apparatus, the actuator moves a lens (a driven part) in a plane and positions the lens at a predetermined location. The actuator disclosed in Patent Document 1 is not to be incorporated into an input device such as a mouse. Particularly, the actuator disclosed in Patent Document 1 cannot be used as a coordinate input device incorporated into an input device such as a mouse, because the actuator cannot detect the position of a part that is moved by an operator to perform an input operation.
As described above, actuators having in-plane mobile parts have been developed. However, there has not been a disclosure of an actuator that operates upon receipt of a signal from a computer, and also functions as an input device for inputting instructions from operators, when incorporated into an input device such as a mouse.